Since Emily posted in her LPSC notes:

"So, so much for Titan. All in all, there wasn't a lot that was new, either new data or new insight. I wish now that I'd skipped the latter part of the Titan session and gone to the rovers, but it was too late for that. The radar story will get more interesting, because after a long hiatus in the acquisition of radar data they are going to be getting a lot more radar passes beginning with the T13 flyby on April 30, so there is much to look forward to there."

I guess I'll go ahead and post the science highlights for the T13 flyby:

T13 - Science Highlights

Imaging Science Subsystem (ISS) – will observe particle properties, vertical distributions (~6 km/px. 0.6 Mbit/frame with 2x2 summing). ISS will also examine wind/cloud motions; (3-12 km/px, 3 images/timestep in CB1 filter to increase SNR), and search for and monitor lightning/aurora. (high-resolution imaging, 50-200 m/px, special targets, emission angles < 45 prefer IR-polarizer (phase 45-110)).

Cassini Plasma Spectrometer (CAPS) – will investigate large-scale and distant aspects of the Titan interaction by observing during entire period around an encounter from 10 to 25 RS.

Composite Infrared Spectrometer (CIRS) –will obtain information on trace constituents in Titan's stratosphere. Integrate on limb at two positions POINTING: Obtain information on CO, HCN, CH4. Integrate on disk at air mass 1.5-2.0. POINTING: -y to Titan, x away from sun.

Ultraviolet Imaging Spectrometer (UVIS) – will observe star Beta Ori as it becomes occulted by Titan’s atmosphere.

Visible and Infrared Mapping Spectrometer (VIMS) – will obtain new high resolution images that will help understand Titan's geology and the fate of CH4.

Magnetometer (MAG) – will investigate large-scale and distant aspects of the Titan interaction by observing during entire period around an encounter from 10 to 25 RS. (23TI (T13)) T13 is an equatorial wake flyby under plasma conditions near Saturnian local midnight with 1852 km altitude at CA. Thus it is very similar to T11 even according to local time.

Magnetospheric Imaging Instrument (MIMI) – will investigate micro-scale and near aspects of the Titan interaction by observing during about one hour period around an encounter. With -Y pointed toward Titan, when within 30 minutes of the targeted flyby, optimize secondary axis for co-rotation flow as close to the S/C -X, +/- Z plane as works with the other constraints on pointing. Also, measure Titan exosphere/magnetosphere interaction by imaging in ENA with INCA (when sun is not in INCA FOV).

Ion and Neutral Mass Spectrometer (INMS) – will obtain data regarding Titan’s atmospheric and ionospheric composition and thermal structure. INMS will also observe the magnetospheric/ionospheric interaction.

Radio and Plasma Wave Spectrometer (RPWS) – will perform observations in the immediate vicinity of Titan, including thermal plasma density and temperature measurements with the Langmuir probe, search for lightning and other radio emissions, characterization of plasma wave spectrum, search for evidence of pickup ions. Langmuir probe within 90 degrees of spacecraft ram at closest approach, co-rotational ram outside of +/- 15 minutes.

RADAR – will perform low and high resolution SAR (Synthetic Aperture RADAR) imagine of Titan’s surface. Additionally, RADAR will collect Altimetry, Radiometry, and Scatterometry Data.

That's what the VIMS highlight always says. Rare data releases, and the ones that do come out are always huge discoveries. Is that an ESA-run instrument?

Bear in mind that these are the highlights for public release; indeed, I believe they're the same ones used in the mission description document that's posted on the flyby page. The really detailed goals are discussed during the closed TOST/SOST telecons.

Notice that RADAR seems to always have a sort of generic description, too. And yes, their description used the word "imagine" instead of "imaging." I didn't want to be cruel and include a [sic].

I can try to fill in some of the gaps in the info for ISS and RADAR. There will be a long E-W SAR swath through central Xanadu. Xanadu's geology continues to be a puzzle, though we maybe making some headway, if you believe Barnes et al.'s cryovolcanism model for western Tui Regio in SW Xanadu (of which I am a co-author, though Jason B. has done all the work except for ISS mosaicking and encouragement). I am a bit confused about their targeting. The beginning of their swath had covered Guabonito, a circular bright feature in eastern Shangri-la, but they may have moved the swath further north. Chuck Wood seemed to think they are now covering Santorini Facula and Veles, two additional eastern Shangri-la bright rings, that may be impact craters filled in with sediment. So hopefully they will get those features so we can pin down what those features are.

Moving on to ISS, we have a high-pixel scale (0.2-0.7 km/pixel) mosaic over Shiwanni Virgae in northern Tsegihi, central Aztlan and Quivira, and eastern Fensal. Not quite sure what we will get out of that data, but it could be useful in constraining the small facula population in central Aztlan and to provide a look at the bright diffuse deposit (landslide? alluvial fan?) northwest of Elba Facula.

It's only slightly less vague but here is another description of the VIMS T13 HIGHRESNA001_PRIME observation centered on 7 degrees latitude and 30 degrees longitude, at a distance of 28,000 km:

"Identification of geologic features including volcanoes, eolian features, and craters, and their correlation with composition. Search for shadows."

Better? Same? Worse?

Don't know how large their footprint is in this area. That would be in central Fensal, a fairly bland area of dark material with a few small (10-25 km) faculae, but nothing major. Depending on how large their footprint is, they may get the northern and southern boundaries of Fensal which contain some interestingly shaped albedo contrasts.

I would post this info but... Well, you know how the VIMS folks are

Personally I was hoping they would point the RADAR further south and target Tui and Hotei. I can understand the desire to pin down some of the features that have the better ISS coverage, but I would think the 5-micron anomalies would be even more desirable targets.

Are there other opportunities in the prime mission for RADAR to cover these areas?

Sad and confused Craig

They won't be able to cover Tui or Hotei, but they swath is a little farther south than I thought and is still in the location that covers Shikoku Facula and Guabonito.

VIMS, if I remember correctly, DID depend upon Italy for a lot of its financing -- its initial inclusion on the instrument payload was provisional, and took a while to finalize.

A off topic question.

When does Cassini view this area, if ever?

After February of 2007.

I heard the SAR imaging will be at low latitudes during T13......but does anybody know exactly where?

RADAR on T13 covers the central brightest areas of Xanadu, which, from what I understand, is important since these regions won't be covered again until late in the primary mission (T43 and T44). There is also outbound altimetry on T13, scatterometry (south of Shangri-La), and new radiometry coverage complementary to TA-T8.

Excellent thanks for the info Alex. Central Xanadu will be really interesting.

Im starting to favour a cryovolcanic origin for the brightness of Xanadu Regio.....or a combination of cryovolcanism and rain cleansing.

I suppose if Xanadu Regio has been a hotspot for volcanism and outgassing in the past, could that have also lead to heavy bursts of methane rain associated with the outgassing?

Four days to go. Cassini's crossing Titan's orbit inbound.

Flyby page is up
http://saturn.jpl.nasa.gov/news/events/tit...60430/index.cfm

Odd I have not been able to access any Cassini website this week.

here is the swath overlain on the current basemap. In addition to central Xanadu, RADAR will also cover portions of eastern Shangri-la, seen repeatedly by ISS. Among the interesting features there are Shikoku Facula (formerly Great Britain; a land of apparent channels), Guabonito (a possible partially buried impact crater), and Kerguelen Facula.

How the encounter go? Not one raw up yet.

Some raw images from T13 are already up - including a great view of the "New Territories", east of Fensal/Aztlan/Quivira!
I can hardly wait for the RADAR data, although - I think - it usually takes something like one week until the first press release.

Cool stuff. More should be down in the next few days.

VP Can we expect processed images soon?

While waiting for the release of the T13 radar data, I came across this beautiful painting of a Titanian landscape from the January 1985 issue of National Geographic – good old innocent pre-Cassini times!
The impact crater on the painting might resemble Guabonito, the broken ring of bright material in the darkness of Shangri-La, which is hopefully covered by the T13 radar (keeping fingers crossed!).
Of course, the real Guabonito is most probably surrounded by a “sea” of sand dunes, and not of liquid hydrocarbons.

Painting by Ludek Pesek © National Geographic Society.

Thanks very much for sharing this, Thorsten.

It was a pleasure, ljk4-1, but the credit actually belongs to Mr. Pesek, (1919 - 1999), a great space artist - especially his works on Mars. Still, it should help us while away the time until the RADAR team releases the first portions of the SAR swath.

The choice of colors in that painting are interesting, because it is close to the 'true' reddish hue assigned to the Huygens DISR images.

I think it's interesting that there are just three other worlds in the solar system with a solid surface and enough atmosphere to make the sky something other than black, and all three of them have orange skies.

(I suppose in the right place at the right time, you would see something besides black in the plumes of Enceladus, Io, or Triton.)

FWIW, it's also interesting that every atmosphere we know of is dominated (>75%) by one of three gases: CO2, H2, or N2. In a universe of infinite variety, some things come up again and again.

There is a very small percentage of 'helium stars' the progenitors of supernova type Ib. (http://seds.lpl.arizona.edu/messier/snr.html)

Crops from the portion of the SAR swath played back Monday are now online. More crops from the rest of the swath, over Xanadu, should be released in the coming days.

Shikoku Facula (formerly Great Britain)
http://photojournal.jpl.nasa.gov/catalog/PIA08426
This is one of my favorite features on Titan and it is nice to see it in a new light, so to speak. The basic shape of Shikoku is visible here, though a few differences from the ISS view are apparent, such as the apparent impact crater in Northeastern Shikoku, which is not associated with an albedo variation, as well as some patchiness to the southern part of the facula. Also note the channels which appear to run from west to east in Shikoku. The ~east-west trending features to the east of Shikoku are dunes.

Guabonito
http://photojournal.jpl.nasa.gov/catalog/PIA08425
Another of my favorite features is visible at the center of this cutout. Guabonito consists of a ring of near-IR bright material within the Shangri-la dark region. In radar, it still appears as a ring of RADAR bright material. I still favor the partially buried impact crater hypothesis, but this data doesn't rule out the possibility that Guabonito is a cryovolcanic caldera. The extreme western margin of Xanadu is also visible in this cut out at the lower right.

RADAR and ISS comparison movie
http://ciclops.org/view.php?id=1996
This short animation (trust me download the Flash file), shows a comparison between the RADAR SAR data taken on Sunday and an ISS mosaic of the same area from T8 (October 28, 2005). Note the differences in Shikoku, particularly with that dark spot in northeastern Shikoku.

Yes, Ludek Pesek was one of the great "reality" space artists. I fondly recall his
work in the National Geographic magazines of the early 1970s. I always end up
comparing other's similar work to his.

It that the same NGM issue which depicts a Venera lander on the Venusian surface?

Marvelous new SAR images. Regarding the ambiguity as to whether the circular features we're seeing are craters or calderas, there was yet another LPSC abstract at http://www.lpi.usra.edu/meetings/lpsc2006/pdf/1659.pdf . It's beginning, however, to look more and more ominously possible that Cassini's coverage of more and more of Titan's surface area may not enable us to understand much more about just what it is we're actually looking at -- for that we'll need higher resolution, which Cassini cannot provide.

(A pity that features on Titan aren't named after famous monsters of myth. In that case we could have "Dracula Facula".)

Absolutely great pictures! Amazing, but the channels appear to be more easily discernable in the ISS pictures than in the RADAR release (especially the “Thames” at the bottom of Shikoku/”Great Britain”. Also, could that be a second, partially degraded, impact crater (middle left at the height of “Wales”)? The image to the left is taken from Porco et al., 2005.

[url=http://www.lpi.usra.edu/meetings/lpsc2006/pdf/1659.pdf]

From Bruce's reference:


Wouldn't a cluster likely occur when a comet-like object from the Kuiper belt broke up before impact? Are not comets a likely source of impact fodder after Titan's resurfacing?

you can't see the crater(?) at all in the visible images! submerged?

Ahhh... lucky number 13 strikes again... Even though we all know it was actually flyby number 14

Does anyone know more about what science data was lost? I was somewhat surprised to see so few high-res ISS footprints in the raws. Also, it's nice they came out and told us openly about the problem -- unlike T7.

I think that the resolution of the SAR data at Shikoku, which if you look at the ISS-RADAR comparison movie you can see that it is very close to the end of the swath (the right edge was just a temporary cutoff until the rest of the data was processed after that movie was made), is only a little bit better than the best ISS data at Shikoku. For example, look at the dark circular spot in NE Shikoku. If you look about one spot diameter south of it, you see a very bright spot (also visible in the ISS image). Below that is a dark channel that runs to the east. If you trace that channel west, it splits in two. Okay, that channel is visible, just barely, in ISS data from T10 I think. so in this area, the sar is low enough in resolution to be comparable with the ISS data. as you go farther east, like with the Guabonito section, the resolution obviously improves. BTW, I don't see that second crater you mention.


Well, it simply means that you have the same type of material (water ice, acetylene, plutonium... ) that shows up as bright in ISS and "blue" in 1.3-2-5 micron VIMS data but can be either smooth or rough. Some how, this smooth area has avoided being filed with dark material.


We lost a lot of our more distant images of titan on this encounter. We also lost half of our high-res mosaic. I head that some of our high phase satellite observations post-T13 may have been lost due to the contingency recovery of part of the Titan C/A data (UVIS occultation, SAR), but some of that is now on the JPL raw images page, so who knows...

Am I correct in assuming the losses were solely due to data being overwritten by subsequent (non-Titan) observations? Those lost high phase observations that you mention would then be lost simply because the s/c team quickly repartitioned the recorder usage so as not to overwrite other, more important data? Or did they simply cancel those observations?

The data that would have been played back Tuesday, will not be played back, instead the SAR and other Titan C/A data was.

Nice to see the new radar data so quickly. I played around with a smoother on the Shikoku Facula image to see whether it makes details easier or more difficult to see. I'll let the forum be the judge though I like some aspects of it.

http://laps.noaa.gov/albers/sos/saturn/tit...08426_sm3x7.jpg

It's also interesting to see the CICLOPS release comparing the ISS and radar. Perhaps a still image highlighting more a merged image of ISS & radar would look interesting? Also, some fancier Fourier type filtering might be applicable to combining the ISS & radar while passing in spatial frequencies in such a way to suppress some of the radar noise. Easy for me to say as I haven't actually tried this.

hmm, interesting.

one mode of comparison I like is to outline the bright and dark boundaries in an area on the ISS image then past those outlines on a co-aligned RADAR view to see how these boundaries line up, for example how they compare to the distribution of longitudinal dunes.

Or take a page from Mel Brooks if the area has high methane concentration, ergo, Flatula Facula.

You know, we may have a new parlor game here.

Regarding the circular features: Impact craters and volcanic calderas are mentioned here, but are these the only possibilities? What sort of appearance would we expect from the remains of an ice/clathrate diapir that slowly made it all the way to the surface, rather like a terrestrial salt dome? (A kraken rather than a vampire?)

[quote name='volcanopele' date='May 4 2006, 06:04 PM' post='52766']
I think that the resolution of the SAR data at Shikoku, which if you look at the ISS-RADAR comparison movie you can see that it is very close to the end of the swath (the right edge was just a temporary cutoff until the rest of the data was processed after that movie was made), is only a little bit better than the best ISS data at Shikoku.

Thanks a lot, volcanopele. That was very informative!

The abundance of channels at Shikoku Facula is quite impressive, when compared to similar RADAR- and IR-bright regions at the same equatorial latitude (such as Adiri from the T8 SAR swath, where there is only one indication of fluid flow (at the NW of PIA03568 – Diverse Geology)).
Could this abundance of channels be somehow related to the topography of Shikoku – but why should that be so much different from Adiri, which also contains mountain ridges/ hills/ elevated terrain?
Or are the channels derived from underground methane released after the formation of the impact crater in NE Shikoku. However they appear to run parallel to the crater rather than starting from it. Furthermore, they seem to be more branched than the rather primitive looking channel features E of Menvra (in the T3 SAR picture PIA07366 - Huygens Landing Site Similarities). So could they possibly be the result of rainfall? Interesting!

However, for people who are fond of channels – like me - I could imagine that the T16 SAR swath at July 22 (which should cover regions close to the – presumably much wetter – north pole) will probably be a dream come true.

hmm, kinda like those lenticulae on Europa. Not quite sure how those would look in RADAR.

The problem with identifying impact craters on Titan is that very few are prestine (if you can call Sinlap prestine, assuming that it doesn't have a central peak due to crustal thicknesss at the time of formation). With Venus, identifying craters was easy since nearly all of them were very classic impact craters, with only a few showing modification since their formation. This is part of the evidence that Venus' surface was catastrophically resurfaced, though you can get the same look other ways. On Earth, in SAR data you can identify vaguely crater-like features as craters because you can go to the site and identify rocks and structures that support that conclusion, a luxury we don't have (yet) on Titan. So the lack of prestine craters and ground truth does make it more difficult to firmly conclude whether a feature is a crater or not. This is especially difficult for ISS since we can only see albedo, a dark material doesn't have to fill the entire floor, making a circular dark spot, and as we found out at Shikoku, dark material doesn't need to fill it at all.


Good point. either there is a difference in climate patterns between this region and Adiri, or these channels are spring-fed, and only small or no springs are found in Adiri. I'll have to take another look at the T8 swath.


Could also be one of our best chances to see a lake in RADAR data, though I would be surprised if some of the very smooth areas in T7, T8, and T13 turn out to be playas.

Oh speaking of which, Emily has posted on her blog a brief description of the Xanadu portion of the T13 swath. The RADAR team presented a giant printout of the swath at the OPAG meeting yesterday, where she got a look at it. She mentions the abundance of mountainous terrain, but without the apparent mountain chains seen in the T8 data. More like the Titan equivalent of the Tibetan plateau (but not THAT high up...). She also mentions an abundance within Xanadu of drainage channels. So I'm sure you'll be happy as a clam tracing out those channels, Thorsten. Hopefully cutouts of parts of the Xanadu portion will be released shortly.

In addition, Emily mentions Dennis Matson's full description of what happened on Monday with the downlink problems. I am just glad that I didn't hear about it until after data did finally start coming down.

Two additional sections of the T13 RADAR swath were released today showing regions in central and western Xanadu:

Xanadu: Rivers flowed onto a Sunless Sea
This portion shows the western boundary of Xanadu. For reference, the facula (bright feature) at center left is the same as the one at top right in PIA08425. There are some differences between the optical Xanadu boundary and the RADAR boundary, particularly in the upper part of the boundary in this cutout, that should be investigated. In western Xanadu, a set of complex, dendritic, bright channels, flowing from north to south, can be seen. Have fun tracing those out, Thorsten. The illumination of this scene indicates that Xanadu is topographically higher than the Shangri-la Sand Sea to the west.

Impact Craters on Xanadu
This view shows central Xanadu. In this area, two impact craters can be seen. The first, near the upper right, has a smooth floor, a central peak, and a broken rim. The second, in the lower left portion of the image, has a visible rim, but no central peak, and appears more degraded and deformed. In addition, other mountainous features can be seen in this area.

Enjoy!

Releasing small portions of the swath are very discouraging. We have still not seen parts of the last radar swath.



I really do hope we seen the whole image soon.

Flowing out from shoreline?.. I prefer to think we see deltas. The river could flow from higher latitudes, where precipitation is relatively abudant.

Absolutely spectacular! Schiaparelli would be delighted!

Since river-like features on Titan are supposed to be named after mythical or imaginary rivers, I hope very much that they name the biggest guy in Xanadu "Alph". And since there are plenty of channels left one could name another "Sarasvati Flumen", after the Hindu- equivalent of Alph.

Did you see, Decepticon, that there is already a global image of the full T13 SAR swath at the T13 Flyby page. Unfortunately, the resolution is only modest – I have difficulties in tracing the location of the two craters from the press release.